#include<iostream> #include<string> #include<iomanip> #include<cmath> #include<vector> #include<algorithm> #include<utility> using namespace std; #define int long long #define endl "\n" constexpr long long INF = (long long)1e18; constexpr long long MOD = 1'000'000'007; struct fast_io { fast_io(){ std::cin.tie(nullptr); std::ios::sync_with_stdio(false); }; } fio; signed main(){ cout<<fixed<<setprecision(10); int N; int SA = 0, SB = 0; vector<int> A, B; cin>>N; A.resize(N); B.resize(N); for(int i = 0; i < N; i++){ cin>>A[i]; SA += A[i]; } for(int i = 0; i < N; i++){ cin>>B[i]; SB += B[i]; } if(N == 2) { if(SA == SB) { cout<<abs(A[0] - B[0])<<endl; } else { cout<<-1<<endl; } } else { int con = SA - SB; if(SA >= SB && con%(N-2) == 0) { con /= N-2; bool flag = true; int con2 = 0; for(int i = 0; i < N; i++){ A[i] -= con; } for(int i = 0; i < N; i++){ if(A[i] > B[i]) { flag = false; break; } if((B[i] - A[i])%2 == 0) { con2 += (B[i] - A[i]) / 2; } else { flag = false; } } if(con2 != con) flag = false; if(flag) cout<<con<<endl; else cout<<-1<<endl; } else { cout<<-1<<endl; } } return 0; }